This invention relates to unsaturated polyester compositions containing a rubber and a calcium carbonate filler.
Molding compositions, particularly polyester thermosetting molding compositions are finding wider application in such areas as automotives, appliances, toys, and other molded items. Their acceptance depends, in part, upon the degree of impact strength the cured molded article possesses. The art teaches that unsaturated polyester compositions have increased impact strength imparted thereto through the use of a rubbery polymer. U.S. Pat. Nos. 4,158,654 and 4,020,036 describe thermosetting compositions comprised of an unsaturated polyester resin, fillers, such as calcium carbonate, additives and a carboxy-containing diene polymer, the carboxy content being shown to further increase the impact strength of the final cured molded composition.
However, there is a need in the industry for even greater impact strength particularly as the emphasis moves from toys and other light duty applications to structural components such as automobile fenders and other load bearing structures in automobiles and appliances. Also these compositions tend to give areas of low gloss in the final molded product which is not like surface problems in other areas of plastic molding, and the cause of which is not understood.